The necessity of custom fitting eyeglasses and their associated frame to an individual wearer of the glasses is well known in optometry. Discomfort associated with ill-fitting glasses is well known often used in commercial advertisements related to marketing of new eye wear. For this reason, it is common practice for an optometrist to carefully and precisely calibrate the dimensions of various critical head contacting points of each eyeglass frame to the widely variable facial characteristics of each wearer.
In a manufacturing or other high eye-hazard environments where the wearing of eyeglasses is mandatory to maintain an acceptable safety standard, it is important that eyeglasses be worn without noticeable or even sub-liminal discomfort so that proper attention can be continuously paid to work at hand. In such environments, it is common for safety glasses to be provided from a general, but usually limited inventory, for people who do not normally wear safety glasses or glasses of any kind.
The variety of over-the-counter and non-prescription eyeglasses, such as sun glasses, is often restricted in sizes available to a customer by the number of different sizes which are commercially available and economically supportable by the volume of glasses sold at each particular store. In the case of reading and other vision correcting eyeglasses, it is as important that each pair of eyeglasses fit properly and provide wear comfort similar to an optometrist fitted pair of eyeglasses.
Customarily, in such circumstances, glasses are available in, at best, a limited number of sizes on each occasion where a new pair of eyeglasses is selected for use by the wearer. It is more often the case that such glasses do not fit each wearer in a manner consistent with needs established by safety and comfort standards. After a period of wear, it is not uncommon to see such a wearer remove the glasses, if only for a moment, to provide relief from some discomfort.
A limited number of safety and non-prescription eyeglasses comprise adjustable features such as wire forms of sides or temples which are bendable to adjust each bow which forms the curved extremity of the side or temple to fit a particular auricular dimension. Slidable adjustments for both temples and bridges are known in the art. However, such adjustments are often imprecise and short lived and become poorly adjusted after a period of continued wear.
It also known in the art to provide a rotary expansion screw coupler for adjusting separatable parts of eyeglasses. Each rotary expansion screw coupler usually comprises a medially disposed knurled portion for relatively facile finger adjustment. Generally, the spatial relation of adjusted parts of the eyeglasses is dependent upon the freedom of movement of the screw coupler, itself, or upon parts separate from the coupler, existing at other parts of the eyeglass frame. As such, long term, stable and spatially precise adjustment is not inherently realized by current rotary expansion screw coupled eyeglasses.